Materi 3 Mekanika Fluida

Summary

This lecture on fluid mechanics delves into the various types of pressure in fluids, including absolute, relative, and vacuum pressure, with real-world applications such as scuba diving. The discussion also explores the effects of pressure on human bodies, like the risks associated with rapid ascent in diving, and the role of pressure in industrial applications, such as manometers for measuring pressure changes. Additionally, the lecture highlights how pressure influences machines, particularly in aviation, and how barometers are used to measure atmospheric pressure. The session wraps up with practical advice on avoiding pressure-related hazards.

Takeaways

• 😀 Fluids exert normal force (pressure) on surfaces, which is measured in Pascals (Pa), and can be large enough to require units like KPa or MPa.
• 😀 Pressure is categorized into three types: Absolute, Gauge, and Vacuum. Absolute pressure includes atmospheric pressure, while gauge pressure excludes it.
• 😀 Vacuum pressure is lower than atmospheric pressure and is used in various applications like isolating rooms for patients with contagious diseases.
• 😀 Fluid pressure at any given point in a static fluid is the same in all horizontal directions at the same depth, and pressure is independent of direction.
• 😀 Pressure increases with depth in a fluid due to the weight of the fluid above, and this is influenced by gravity.
• 😀 The pressure in a fluid is proportional to its density and the depth at which the measurement is made, a concept known as hydrostatic pressure.
• 😀 In scuba diving, pressure increases with depth, and sudden changes in pressure when surfacing can cause significant harm to the body, including embolism.
• 😀 Boyle’s Law explains that the volume of a gas is inversely proportional to pressure. In scuba diving, rapid ascension can cause a gas's volume to expand, leading to physical dangers.
• 😀 Pascal's Law states that pressure applied to a confined fluid is transmitted equally in all directions. This principle is used in hydraulic systems.
• 😀 A manometer is used to measure fluid pressure by observing the change in height of a fluid column. It is used for measuring pressure in various engineering applications.
• 😀 Barometers are devices that measure atmospheric pressure, and variations in atmospheric pressure with altitude can affect various phenomena, such as cooking times or the performance of machines.

Q & A

What is fluid statics in the context of fluid mechanics?

Fluid statics is the study of fluids at rest. It deals with the forces and pressures in a fluid that is not moving, particularly the concept of pressure exerted by the fluid on its surroundings.

What are the units used to measure pressure?

Pressure is commonly measured in pascals (Pa), where 1 Pa equals 1 Newton per square meter. In practical applications, pressure is often measured in kilopascals (kPa) or megapascals (MPa). Other units include atmospheres (atm), bar, and pounds per square inch (psi).

What is the difference between absolute and relative pressure?

Absolute pressure is the total pressure measured relative to a perfect vacuum. Relative pressure, on the other hand, is the pressure measured relative to atmospheric pressure. If a pressure gauge reads zero, it is measuring relative pressure.

What is vacuum pressure?

Vacuum pressure refers to the pressure that is below atmospheric pressure. It occurs when the pressure inside a container is less than the surrounding atmospheric pressure, creating a vacuum environment.

How does pressure change with depth in a fluid?

Pressure increases with depth in a fluid due to the weight of the fluid above. The deeper you go, the greater the pressure, as the weight of the fluid above increases. This is described by the hydrostatic pressure equation.

What factors influence pressure in a fluid?

Pressure in a fluid is influenced by depth (height of the fluid above the point of measurement), the density of the fluid, and the gravitational acceleration acting on the fluid.

How does the density of a fluid affect pressure?

The density of a fluid affects the pressure at a given depth. Denser fluids, such as mercury, exert greater pressure at the same depth compared to less dense fluids like water, due to the increased weight of the fluid.

Why does pressure in a fluid remain constant along horizontal planes?

Pressure in a fluid at rest is the same at all points on a horizontal plane at the same depth. This is because the fluid exerts equal pressure in all directions on points at the same depth due to the balance of forces.

What is the connection between scuba diving and fluid pressure?

When scuba diving, pressure increases with depth. The pressure on a diver's body is significantly higher underwater than at the surface. As the diver ascends, the pressure decreases, and the volume of air in the lungs expands, which can lead to discomfort or dangerous conditions like embolism if ascended too quickly.

How does Pascal's principle apply to fluid mechanics?

Pascal's principle states that a change in pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid. This principle is used in hydraulic systems, where small applied forces result in large output forces due to the pressure transmission.